(ADV7282AM)CVBS-diff lock problem.

Hi !

Our customer have some trouble at their ADV7282AM system.

They are not using ADI EVAL board. They are using their own PCB board.

But the script is 100% same as ADI recommend script.

We are trying to connect customers video source to ADI EVAL board next week.

They will use ADV7282AM for automotive rear camera interface.

Their problem is this.

*************************************************************************************************************

①Immediately after register setting, seemingly normal color bars are displayed.
 However, since analog noise occurs sporadically, it seems that some problems already exist.

②When ADV7282A-M lock to CVBS-Diff, the status bit is this.

 0x10 => 0x05

 0x11 => 0x43

 0x12 => 0x00

 0x13 => 0x69

③After a while, the image display is disturbed. (It may be several seconds, sometimes a couple of minutes later)

 When checking the status register when the video display was disturbed, the lock was lost.

④When several minutes elapsed again, there was a case where it returned to a normal image.

⑤When resetting the IC and setting the register again, a normal color bar is displayed and return to ① as I wrote above.

We already checked that ADV7282AM AIN pin clamp looks there is no problem.

We checked CLK jitter but there was no problem.

*************************************************************************************************************

We will confirm the input signal in more detail.(ex. sync, sub carrier...)

They are using fast switch mode and the disable fast switch after system start but nothing changed.

We asked to my customer to change VID_STD to NTSC-M buy the problem didn't disappear.

They are connecting 

DVD player => ADA4433-1(change single to differential) => ADV7282AM => SoC > Monitor

ADA4433-1 circuit is this.

(ADA4433-1) To connect ADA4433-1 to ADI Video decodor 

Also they changed 150Ohm register to 75Ohm.

(Video decoder)When inputting full differential, is the network resistance really 150 ohm? 

We already know that ADV7282AM status bit is something wrong and when they use free run mode there is no problem so we think it is not SoC or Monitor problem.

Do you have any idea what is the reason for this problem?

Do you have any advice for this?

Are there similar experiences?

Best regards

Kawa

  • Hi!

    Can somebody help about this?

    It will be a great help if you help me.

    Best regards

    Kawa

  • Hi!

    Thank you for your reply.

    Since it is confirmed by register read back that the lock has already been removed, we will confirm with the customer whether to use the INT pin.
    Also, it is confirmed that the output is NTSC - M, but I will check if it can be locked with AUTO DETECT.

    How about using some Antialiasing Filters or other filter?

    Best regards

    kawa

  • Hi,

    For lost lock :0x10 -0x07

    The following example will describe how to set the interrupt pin to go from a
    high state to a low state when the ADV7282 has lost lock to the inputted video.The interrupt will remain low until cleared.
    1) Enter the Interrupt/VDP Sub Map by setting register 0x0E bit [5] to 1
    2) Program the interrupt to drive low when active and to stay low until cleared: In register 0x40 write 0xD1
    3) Unmask (i.e. activate) the unlock interrupt: set register 0x44 bit[1] to 1.
    4) Clear the interrupt by writing 1 to register 0x43 bit [1]. (Note the bit will automatically reset to 0 after being written to).
    5) Re-enter the User Map: set register 0x0E bit [5] to 0.
    Note this should be run after a normal script has been run on the ADV7282.
    Please refer https://ez.analog.com/docs/DOC-3108. Believe this would be more helpful for you.

    Line length is nonstandard: 0x12 -0x10

      Try setting up the ADV7282 to auto detect the input standard and enable all standards to be detected.
    If the camera is outputting a non-standard version of NTSC,then the ADV7282 may not be able to lock to it.
      Please refer https://ez.analog.com/thread/92777-adv7188-line-length-recognition.

    Thanks,

    Poornima

  • Hi,

     The ADV7282 have anti aliasing filters that are basically low pass filters designed to remove high frequency noise (outside analog video bandwidth) on the Ain lines.These filters have a -2 dB cut off of 10 MHz.
     For anti aliasing ,luma and chroma filter details,Please refer page 11,22,25 in adv7282a user guide

       

    The ADV7180/ADV7182/ADV728x video decoders are designed to be low cost analog to digital video decoders and as such they only have 2D comb YC separation filters.2D comb filters are good at separating the luma and chroma information.

      3D comb will result in fewer artifacts output to the screen. However  a number of frames of video need to be stored in an external SDRAM chip in order for the 3D comb filter to work. This will add a delay from inputted video to outputted video.

    Thanks,

    Poornima

  • Hi !

    Thank you for your reply.

    I know what AA filter is.

    But there is no detail about filter.

    Can you tell each specification about these filters?

    Also I am not asking about each filter.

    Do you have any idea what cause this un-lock problem?

    Best regards

    Kawa